共查询到20条相似文献，搜索用时 218 毫秒
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采用分子束外延技术（ＭＢＥ）生长了具有ＧａＡｓ／ＡｌＧａＡｓ超晶格缓冲层的单量子阱和多量子阱材料．采用ＧａＡｓ／ＡｌＧａＡｓ超晶格缓冲层掩埋衬底缺陷，获得的量子阱结构材料被成功地用于制作量子阱激光器．波长为７７８ｎｍ的激光器，最低阈值电流为３０ｍＡ，室温下线性光功率大于２０ｍＷ． 相似文献
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通过激光熔覆Fe基熔覆材料,在钢和铸铁表面获得了组织均匀、细化、无缺陷的激光熔覆层,这种熔覆层具有较高的显微硬度和优异的耐磨性。 相似文献
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利用液相等离子体电解渗氮技术对奥氏体不锈钢和球墨铸铁进行渗氮处理,比较了两种金属渗氯前后的硬度分布.实验结果表明:同样实验条件下,不锈钢渗氮后的硬度比球墨铸铁渗氮后的硬度要高.根据显微分析和SEM分析可知,两种材料表面生成的渗层的形态不同是造成这种结果的主要原因. 相似文献
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本文的主要目的是研究注塑模具钢自动研磨与球面抛光加工工序的可能性。而完成这种注塑模具钢PDS5的塑性曲面的加工是在数控加工中心实现的。目前,此项研究已经完成了磨削刀架的设计与制造。其中,最佳表面研磨参数是在钢铁PDS5的加工中心测定的。对于PDS5注塑模具钢的最佳球面研磨参数而言,其是以下因素的一系列的组合：研磨材料的磨料为粉红氧化铝．进给量500毫米／分钟,磨削深度20微米,磨削转速为18000R2aM。如果用优化的参数进行表面研磨,表面粗糙度Ka值可由大约1．60微米改善至0．35微米。而用球抛光工艺和参数优化抛光,则可以进一步改善表面粗糙度Ra值从0．343微米至0．06微米左右。在模具内部曲面的测试部分中。用最佳参数的表面研磨、抛光,曲面表面粗糙度就可以提高约2．15微米到0．07微米。 相似文献
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5083铝合金是AI-Mg系防锈铝中的典型合金,要用于模具制造业、造船业、运输业,是制作船板、船外壳、燃料储存罐等的重要材料之一。本文以5083铝合金板材为研究对象,利用金相显微镜、硬度计、电导仪等实验设备,分析了退火保温时间对5083铝合金板材再结晶过程及性能的影响规律。实验结果表明:在退火温度(565℃)时,随着保温时间从15min增加到360min,板材的晶粒尺寸从23.5μm逐渐增大到59.5μm,板材的硬度从82.7HV降低到72.5 HV,板材的电导率从27.2%IACS升高到27.8%IACS。退火保温时间对板材电导率度的影响规律与保温时间对板材组织的影响规律基本相似。 相似文献
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具有纳米结构表层的纯铁和38CrMoAl钢的渗氮 总被引：7，自引：0，他引：7
通过表面机械研磨技术(SMAT),在纯铁和38CrMoAl钢样品表面产生大量的塑性应变,致使其表层晶粒细化至纳米量级.随后的气体渗氮实验表明,纳米纯铁和38CrMoAl钢发生渗氮反应的温度大大低于传统粗晶材料(＞500℃),分别降至约300℃和400℃.这种低温渗氮过程不仅有利于降低渗氮工件的变形和能耗,也为选择性渗氮技术的实现提供了新途径. 相似文献
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根据应用耗散结构理论和人工神经网络确定的热力参数稳定区以及晶
粒度演化的状态空间模型,应用最优控制理论确定保证获得要求组织的GH4169合金的最优轨
迹,即热力参数随时间的变化规律,以便获得晶粒细小的GH4169合金锻件。通过变分法根据
有限元数值模拟结果和材料最优轨迹优化等温锻造用液压机滑块速度随行程变化曲线,使工
件内热力参数变化接近材料最优轨迹,以获得优质的GH4169合金锻件。计算结果表明,本文
提供的方法可有效控制等温锻造过程中工件内热力参数的变化,从而优化锻件的显微组织。 相似文献
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对磨削强化技术进行了计算机仿真与实验分析,并将结果进行对比验证,温度场的有限元计算表明仿真结果与实验结果基本相符,提示磨削强化过程的计算机仿真可以基本代替成本高昂的实际磨削强化试验,不仅大大节省了研究成本,而且有望对磨削强化结果进行预测。 相似文献
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褶皱变形应力场对断裂控制作用的有限元模拟 总被引：2，自引：0，他引：2
有限元法作为一种求解连体力学问题的有效方法,已经广泛应用于地质领域,本文对软硬夹层的紧闭褶皱的变形应力场进行了二维有限元数值模拟。数值模拟结果表明,在本文的模拟条件下,裂隙的发育位置受破裂指标Fn大于3．0的高值点控制．高值点的密度决定了断裂发育的多少：裂隙的延伸方向与模拟的剪切应力方向一致：裂隙的前端具有代表应力集中的Fn指标值的高值点,断裂沿此生长;当断裂延伸至褶皱核部发生分又与合并时,应力梯度下降,应力对断裂的控制能力减弱。研究结果对于有限元法应用于实际地质问题具有重要意义。 相似文献
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The primary objective for modeling of machining processes is to develop a predictive capability of machining performance in order to facilitate effective planning of machining operations. This capability leads to faster implementation, higher performance, quality at a lower cost. This comes about due to improved selection of machining parameters, optimal fixture design and the avoidance of tool failure. The simulation system presented simultaneously considers the effect of cutter geometry, the cutter's initial position errors, workpiece geometry, machine tool dynamics, and workpiece/fixture system dynamics on the machining process.The integration of all of the above in one model provides an off-line tool to simulate and optimize the machining parameters and the fixture configuration cutting both lead and production time. The modular nature of the simulation system presented allows for the study of many different machining processes. The cutting forces in this system are modeled using a mechanistic approach. NURBS curves and surfaces are utilized for the geometric modeling and simulation of the machining process. While a finite element method is used to model and analyze the workpiece/fixture dynamics. Two case studies are presented to demonstrate the practical application of the presented simulation. The first case presents the optimization of the fixture configuration of a generic automotive component. While the second case presents the results of simulations performed on a novel mill/grind machining process. This process is a combination of face milling and grinding in one operation. Some simulated results are presented along with experimental validation. 相似文献
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Sohrab Enayati Seyed Ali Asghar Akbari Mousavi Seyed Mohammad Ebrahimi Majid Belbasi Mostafa Sultan Bayazidi 《Journal of The Franklin Institute》2011,348(10):2813-2822
In this study, the hot backward extrusion of Ti–6Al–4V alloy is considered by finite element analysis and experiments. The effects of reduction and initial billet temperature on the force required for extrusion, on the maximum strain produced and on the formation of surface cracks are discussed. The simulation results show that the increase of temperature at high reduction is considerable and that can be reached 150 °C in the billet and punch interface. Moreover, the maximum strain is predicted at the interface of billet and punch. The study shows that the temperature rise and plastic deformation may induce surface cracks. 相似文献
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采用有限元强度折减法与极限平衡法对边坡的稳定性进行分析,并对两者所确定的安全系数以及滑动面的情况进行比较,解决了极限平衡法不能反映坡体塑性变形趋势以及模拟的滑动面与实际不吻合的问题。 相似文献
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为了研究口模出口高度变化对螺杆分配机头内部流场和挤出均匀性的影响,参数化有限元分析技术贯穿于螺杆分配机头CAE仿真的全过程,采用VISUAL C＋＋和APDL语言开发出专用有限元前处理程序和特殊加载宏,调用ANSYS对螺杆分配机头流道内部流场进行三维有限元模拟与分析。分析结果表明：口模出口高度变小将增加流道内的流动阻力,显著增大狭缝流道内各部分区域过渡截面中间层节点的压力值和口模出口的挤出速度值。当口模出口高度调节较大时,有必要重新调节阻尼块以提高速度分布的均匀性。 相似文献
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Understanding the mechanical properties of optically transparent polydimethylsiloxane (PDMS) microchannels was essential to the design of polymer-based microdevices. In this experiment, PDMS microchannels were filled with a 100 μM solution of rhodamine 6G dye at very low Reynolds numbers (∼10−3). The deformation of PDMS microchannels created by pressure-driven flow was investigated by fluorescence microscopy and quantified the deformation by the linear relationship between dye layer thickness and intensity. A line scan across the channel determined the microchannel deformation at several channel positions. Scaling analysis widely used to justify PDMS bulging approximation was allowed when the applied flow rate was as high as 2.0 μl/min. The three physical parameters (i.e., flow rate, PDMS wall thickness, and mixing ratio) and the design parameter (i.e., channel aspect ratio = channel height/channel width) were considered as critical parameters and provided the different features of pressure distributions within polymer-based microchannel devices. The investigations of the four parameters performed on flexible materials were carried out by comparison of experiment and finite element method (FEM) results. The measured Young''s modulus from PDMS tensile test specimens at various circumstances provided reliable results for the finite element method. A thin channel wall, less cross-linker, high flow rate, and low aspect ratio microchannel were inclined to have a significant PDMS bulging. Among them, various mixing ratios related to material property and aspect ratios were one of the significant factors to determine PDMS bulging properties. The measured deformations were larger than the numerical simulation but were within corresponding values predicted by the finite element method in most cases. 相似文献
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Hameed A. Elnaggar Raymond J. Krizek Gabor M. Karadi 《Journal of The Franklin Institute》1973,296(5):323-337
The effect of non-Darcian flow on the consolidation behavior of clay soils is studied, and its role in the extrapolation of laboratory test results to field problems is evaluated. This is accomplished by postulating a reasonably general four-parameter velocity-gradient relationship which, by proper choice of parameters, is capable of characterizing much of the published experimental data; then, this relationship is combined with the standard assumptions of classical consolidation theory to develop a nonlinear parabolic partial differential equation, which is solved by use of a finite difference technique. The stability and convergence criteria for related linear and quasi-linear equations are empirically extended to the associated nonlinear equations, and a comparison is made between various explicit and implicit finite difference schemes, with the result that a sufficiently accurate and more economical numerical solution is obtained by use of an explicit scheme. Typical solutions for various specific cases confirm and offer an explanation for the well-known phenomenon wherein the time rate of consolidation is found to decrease as the load increment decreases; also, the thickness of the consolidating layer is shown to affect the dimensionless time rate of consolidation. These conditions indicate that laboratory consolidation test results can be applied to a field situation only if appropriate stress and thickness corrections are made. 相似文献